There are a very limited number of Slam Dunk merchandise available on the web. Below is the few I have found through days and nights of surfing and searching, please let me know if you have found others.

Inoue Takehiko Slam Dunk Illustrations

You can get this at AnimeBookStore.com! They have a special sale going on right now, so if you get this book, I think you are also allowed to pick two more art books for free~

Good luck in your hunt for Slam Dunk goodies! I will post more stuff in the next couple of days.